Water tank



FIG. 1 is a perspective view of a water tank, showing the new design;

FIG. 2 is a front elevational view thereof, the rear elevational view being a mirror image thereof;

FIG. 3 is a left-side elevational view thereof, the right-side elevational view being a mirror image thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines showing a metallic cover in FIG. 1 depict environmental matter, and form no part of the claimed design. 

We claim the ornamental design for a water tank, as shown and described. 